Piezo elements can, however frequently not be used or can only be used insufficiently due to their mechanical properties and the limited stretchability. The manufacturing costs can also be too high.
Attempts have thus been made in the past to provide actuators with dielectric elastomer plastics. In this respect, however, due to the high elongations, there are problems with the electric contact and connection of the required electrodes which should be preset under all conditions of use.
The required contact voltages are in a region of 100 kV which can frequently not be controlled or used.
The properties of the material for the dielectric part and the electrodes also differ considerably in many points, which has a particularly unfavorable effect with changed conditions of use or environment.
Usually, metal electrodes are used which, however, have completely different mechanical properties than the relatively soft elastomers. The operation of such actuators therefore usually suffers under the failure of the electrodes.
With highly stretchable elastomers, electrodes should have a similar stretching behavior. Electrodes are therefore manufactured using electrically conductive graphite flakes which are applied to polymer surfaces with a silicone oil. In this respect, however, an actually dry “actuator” has a partly liquid coating applied. This is, however, very unfavorable in a stack structure with an alternation of electrodes and polymer layers. Electrodes formed in this manner are very slick and therefore represent mechanical weak points. In addition, the optical transparency is substantially impaired.
It is known for the formation of optically transparent electrodes which can be used, for example, in organic light emitting diodes (OLEDs) to apply and dry carbon nanotubes (CNTs) in a dispersion so that they are formed in layer form on the luminous organic layers and are in this respect also electrically conductive. The CNTs are in this respect included in a relatively high proportion in an organic matrix, with a compromise having to be made between electrical conductivity and optical transparency with regard to the respective proportion of CNTs and the electrode thickness.
The electrodes manufactured in this manner likewise have greatly different properties from the other components of such OLEDs.
It is known from T. Sekitani inter alia from “A Rubberlike Stretchable Active Matrix Using Elastic Conductors”, Science Express Online, Aug. 7, 2008, to manufacture electrically conductive flexible elements from plastic which are electrically conductive and can simultaneously be stretched. In this respect, CNTs should be added into liquid vinylidene fluoride-hexafluoropropylene with an addition of ionic 1-butyl-3-methylimidazolium bisimide and the mixture thus obtained should then be applied to a glass support. The composite material obtained could then be connected to stretchable silicone rubber. The electrical conductivity can be increased by a high proportion of 20 mass percent of CNTs. The electrically conductive part with the CNTs and the silicone rubber, however, also again have mutually different properties and form a material composite of different materials having different mechanical properties, whereby such actuator elements have a shortened service life or degraded properties.